(a) Technical Field
The present invention relates to a device for measuring uneven wear of starter brushes for a vehicle and, more particularly, to a device for measuring uneven wear of starter brushes for a vehicle which can accurately measure and compare the lengths of the starter brushes and easily determine whether or not eccentricity of an armature occurs.
(b) Background Art
A starter motor is one of the component parts of a vehicle, which converts electrical energy of a battery into mechanical energy to start an engine.
The starter motor basically comprises an armature, a yoke, a permanent magnet, a brush, a bearing, and a shaft. The shaft connected to an engine by means of a worm gear plays a role in transferring power to the engine.
In general, the starter motor is operated to start the engine and requires a high torque. It thus has a tendency to more easily get out of order than the other motors of the vehicle.
If the starter motor gets out of order, it should be replaced with a new one. However, since the starter motor has a structure similar to an ordinary motor and the main trouble occurs in limited areas, it is easy to recycle the starter motor. Accordingly, recycled goods are frequently used instead of new ones.
The main trouble areas are an armature commutator and a brush portion. When the two portions are in direct contact with each other and rotated, abrasive wear occurs.
Especially, if eccentricity is present in the armature, uneven wear, in which only one or two of four brushes are serious worn, occurs. As a result, vehicle vibration is generated and power transmission efficiency is reduced.
At present, recycling manufacturers determine whether or not to recycle the worn brushes by visual inspection and dispose of them if not recyclable.
However, since the visual inspection is conducted in a way that an examiner measures the lengths of the brushes by his naked eyes, it is difficult to accurately inspect the brushes and the variation is quite large according to the workers.
As a result, brushes that should be disposed of may be reused, which causes quality problems in the recycled starter motors. Alternatively, brushes that should be reused may be disposed of.
Accordingly, some of these recycling manufacturers do not reuse the brushes but replace all brushes with new ones. The reason for this is that it is difficult to ensure the quality of the reused brushes due to the large variation according to the workers and the unit price of the brush is not high.
When the worn brushes are all replaced with new ones, no inspection is made separately and thus causes a substantial problem.
For example, if four brushes are worn uniformly as shown in FIG. 5, it is determined that there is no eccentricity in the armature and hence there is no problem. Whereas, if uneven wear occurs between the four brushes as shown in FIG. 6, it will cause a problem since the uneven wear means that eccentricity is present in the armature.
Here again, there is a cause (eccentricity of armature) and effect (uneven wear of brushes) relationship between the armature and the brushes.
Accordingly, if the unevenly worn brush is replaced with a new one, there is no serious problem in the brush in itself; however, it causes various problems such as vibration generated in the field due to the eccentricity of the armature.
Meanwhile, there is a method of measuring the eccentricity of the armature. However, expensive and very precise equipment is required to measure the delicate eccentricity and a lot of time and cost are required to set the positions of the armature, yoke, and permanent magnet one by one. Accordingly, the conventional method of measuring the eccentricity of the armature is not applicable to the existing recycling manufacturers.
Another method is to measure uneven wear of starter brushes. However, since the method is applied only to the brushes without setting the armature, yoke, and the like, it requires less time and cost. Moreover, since the method measures only the lengths of brushes, the measurement equipment is relatively inexpensive. Furthermore, although the method indirectly measures the eccentricity of the armature, it is believed that it is better than the method of measuring the eccentricity of the armature in terms of efficiency.
The information disclosed in this Background section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.